This application is a national stage application of International Application Number PCT/EP00/08432 filed on Aug. 30, 2000 which claims priority to German Application No. 19942508.6 filed on Sep. 7, 1999.
1. Field of the Invention
The invention relates to a method and a device for the transmission of control and/or sensor signals between an electronic control and/or data receiving means and a pneumatic device, which are connected together by way of a pneumatic line of flexible plastic material.
2. Description of the Prior Art
For the control of pneumatic equipment, such as valve arrangements, cylinders, drives and the like, there is on the one hand the requirement for the supply of compressed air by way of a pneumatic line and on the other hand for electrical supply lines for the supply of electrical control signals and furthermore return lines for the return of sensor signals. If a plurality of control devices, such as valves, and sensors are arranged on one pneumatic device there is a corresponding increase in the number of electrical lines, something which frequently means that there is a somewhat chaotic arrangement of lines involving high costs for the installation, servicing and repair of such equipment.
Although the German patent publication 19,526,459 discloses the control of a bus station on a valve station having a plurality of valves by way of a bus line, by way of which sensor feedback signals may also be communicated, in this case additional electrical power supply lines and the pneumatic line are required so that there is a considerable complexity of installation.
Although the German patent publication 3,147,339 A1, the German patent publication 3,209,189 A1 and the German patent publication 4,115,403 C2 disclose the transmission of control or sensor data by way of a metallic tube supply system using ultrasound, this method is generally not applicable to pneumatic lines, which normally are made of plastic material
Accordingly one object of the present invention is to provide a method and a device by means of which the number of connecting lines leading to a pneumatic device to be controlled may be substantially reduced and installation may be simplified.
The advantage of the device of the invention is more especially that the control information and the sensor signals are simultaneously transmitted using the pneumatic line, which is present in any case present so that special lines are no longer necessary for this. In this case the transmission is by way of the gaseous medium in the form of acoustic signals, microwaves or changes in pressure. Accordingly the transmission of signals is possible in the case of plastic lines as normally employed. It is an advantage here to employ at least one first converter for the conversion of electrical signals into acoustic signals, microwave signals or changes in pressure, and at least one second converter for conversion of such signals into electrical signals.
Transmission of the data takes place bidirectionally in order for example to be able to transmit control signals in one direction and sensor signals in the other direction. For bidirectional data transmission both the control and/or the data receiving means and also the pneumatic device is provided with a first converter and with a second converter, one first converter and one second converter being able to be respectively in the form of combined bidirectional converters. In practice more especially piezoelectric, but also inductive or capacitive converters may be used for this purpose.
For the transmission of different control or sensor signals different frequencies and/or signal sequences and/or pressure modulation and/or pressure pulse sequences are suitable.
In order to dispense with having separate electrical supply lines leading to the pneumatic device, the transmission of power supply energy for the operation of electrical loads on or inside the pneumatic device is also by way of the gaseous medium in the line.
For this purpose it is convenient to provide means for the conversion of acoustic signals or pressure changes or pressure into electrical power energy in or on the pneumatic device.
The acoustic signals or pressure changes are converted in the pneumatic device preferably using the piezoelectric effect at least partially into electrical energy, for which purpose use is preferably made of a piezoelectric converter. As an alternative to this inductive or capacitive converters or an oscillating piston device may be utilized.
In an alternative design it is possible for the electrical power supply energy to be produced in the pneumatic device also by using of the gaseous medium for driving a microturbine or, respectively, a microgenerator device.
In order to ensure that the electrical supply power is continuously available, for instance in the case of a transient peak in the energy requirement, it is an advantage to provide a storage means, and more especially a capacitor or a storage cell, for the storage of the electrical supply energy produced in or on the pneumatic device.
A converter more particularly in the form of a microcomputer in or on the pneumatic device may advantageously serve for the conversion of the transmitted signals into control signals for at least one control means, for example a valve, in the pneumatic device and/or for the conversion of sensor signals into signals to be transmitted by way of the pneumatic line.
The control and/or data receiving means is preferably in the form of a bus station connected with a data bus. In this respect a plurality of pneumatic devices can be connected with this bus station by way of pneumatic lines directly or by way of branch connections.
In the case of systems of large size it is possible furthermore for a plurality of bus stations to be connected with the data bus, which are respectively connected with at least one pneumatic device.
The at least one converter and the means for the supply of electrical power energy are preferably integrated in the pneumatic device so that the arrangements are compact and for complete installation merely have to be connected by way of a single pneumatic line.
Working examples of the invention are illustrated in the drawings and will be explained in the following description in detail.